Various types of expanding and contracting chucking devices and/or clamping devices of similar character have been used in factories and workshops for the clamping of rotatable workpieces. These workpieces may then be machined, ground, or polished in a variety of shop operations all of which require the workpiece to be precisely rotated. For reasons of precision and accuracy mandrels capable of expansion or contraction used in the past were able to accommodate workpieces within a very limited range of diameters due to the loss of contact grip which occurs when the mandrel is expanded or contracted beyond its designed expansion limit. Because of this limitation, it is necessary to replace the mandrels (or inserts) in shop lathes, etc. at the end of each production run in order to accommodate the next run of workpieces which have a different diameter.
Previously when this situation arose, the entire mandrel was removed from the mounting spindle of the lathe to which it was attached, usually by removing several cap screws from the mounting boss of the mandrel, and the replacement mandrel is precisely located against the spindle mounting device, the mounting holes aligned, and the fastening cap screws replaced. This replacement operation may require considerable shop time.
Various types of quick change mandrels and chucks have been proposed for use in industry in the past and the designs have used a clamping mechanism which encompass the use of balls, ramps and springs which function in a manner similar to the principle used in air line chucks. Most of the quick change devices are relatively small and are best suited to small power operations. See U.S. Pat. Nos. 4,861,201, 4,749,316, 4,743,145, 4,309,042, 4,290,617 and 4,273,344 for a variety of the prior art devices. A slightly larger quick change chuck is shown in U.S. Pat. No. 5,326,114.
These devices while functioning in a quick change manner do not have the convenience and the power transmission capability of the mandrel type chuck of this invention.
In workshop operations where powerful machinery is used for stock removal or surface profile forming, some type of mandrel must be used which will tolerate the heavy mechanical forces involved. For replacement of chucks and mandrels of the power handling capability of the devices of this invention, the classical approach to such a change has usually involved removing the complete mandrel or chuck from a mounting spindle of the lathe and re-mounting another chuck or mandrel on the spindle mounting device. Because of the nature of the machinery involved, the ever presence of foreign material makes the replacement operation difficult and during the change operation, sometimes the mounting bolts may be misplaced or lost. The weight of the mandrel device also has a tendency to complicate the replacement operation.